How Does M+R Work?

Scenario: Vendor Code Reconciliation

Suppose you are a systems manager, and your site runs Release N of a vendor product.

You have applied fixes and modified the vendor product to customize it for your users. When the vendor announces the next release, (N+1), your users want it installed immediately. You are now faced with a version migration filled with these complications:

If you install release N+1 as is, your own custom modifications are regressed.
Some of the vendor’s fixes duplicate your own changes, so not everything you have done must be reapplied.
It took you many months to evolve modifications for release N, and neither you nor your users want to wait that long for the next release customization.
The upgrade job looks long, painful, and error-prone—particularly if the vendor has renumbered the source code lines. You need a fast, intelligent method to blend the vendor’s upgrades and your custom modifications into a working product.

Solution: M+R

M+R can handle this problem. First, you have to identify the source files (the base version and derivatives) to M+R.

The base is the Release N of the vendor product.
One derivative is the current production library that contains your customizations.
The other derivative is the Release (N+1).

Then, you run M+R, which performs the following steps:

Compiles member lists of the base/derivative libraries and matches same-named members in version sets.
Loads the chosen base members and the derivatives’ members into storage.
Compares the base version with each of the derivatives, records the differences, then compares and combines them.
Stores the base version and the differences in the M+R work-in-suspense file.
Identifies conflicts and single changes.
Calculates the degree of complexity of the reconciliation effort, and stores the relevant statistics.
Displays a full view of the merged versions, formatted graphically and in color, for reconciliation.
The following figure illustrates schematically how M+R reconciles different releases of software.

M & R Reconcile

The following table shows the steps that you must take in order to merge and reconcile.

Steps	M+R Function	Meaning
1	M+R compares Version A to Version B	This comparison identifies the changes and modifications added to the vendor code release by your company.
2	M+R compares Version A to Version C	This comparison identifies vendor’s changes between Release N and Release N+1.
3	M+R merges and combines the differences with Version A	By presenting the combined versions for browsing and editing, you can see the differences between all the versions.
4	Reconcile the changes	Now, you reconcile the changes to create a conflict-free consolidated version that includes Vendor Software Release (N+1) and your company‘s modifications.
5	M+R extracts the reconciled code and creates Version D	Version D is the new production software containing the new (N+1) vendor release plus all the needed customization minus those user modifications (fixes) that have already been addressed in the (N+1) release.